banked roads, or swerving to avoid accidents. Full loads also must be snug and adequately
braced to reduce stress resulting from impact against loading docks, braking, acceleration, and
sway.
D. Shipping by water is different. As illustrated in Figure 6-1, a ship at sea may move in all of
the following six directions: pitching about a vertical axis; yawing about a vertical axis; rolling
about a longitudinal axis; surging in a fore and aft motion; swaying in a side-to-side motion; and
heaving in an up and down motion. In addition, wave impact or water entry into faulty
containers can affect loads and damage containers.
E. Rail transport includes railcars, TOFC, and COFC. Typical forces encountered in the rail
transport environment include vertical, sideward, and lengthwise pressures.
1. Vertical pressure or vibrations, over and above the overhead weight of the load, are the
most numerous forces but are small in magnitude and cumulative. Generally, the damaging
action from vertical pressure or vibrations is absorbed by interior cushioning or bracing within
the individual package or container.
2. Sideward pressure toward the sidewalls happens when a car rounds a curve, an action that
tends to move the containers out of alignment with adjacent containers. Also, sideward pressures
tend to crush the containers on the off-side as the car rounds a curve. Although those pressures
are of small magnitude, if the containers are out of alignment, subsequent lengthwise forces can
cause damage because of uneven distribution of pressure.
3. Lengthwise forces on the load result from cars accelerating or decelerating at a rate
different from that of the whole train because of coupler slack. The impact of lengthwise force is
normally negligible, since coupling impact is regulated by Title 49 CFR. Hazardous materials in
railcars are to be coupled with no more force than is necessary to complete the coupling.
Additionally, Title 49 CFR, section 174.83, states that no railcar moving under its own
momentum may strike a flatcar carrying a placarded trailer or freight container (humping). Other
forces affecting rail transport include suspension system and track dynamic vibration, and sway,
a side-to-side motion resulting from curves or uneven track.
F. While loading of aircraft may not be an installation responsibility, personnel should be
aware of some of the complexities involved and that only properly trained and designated
individuals can certify proper packaging and marking of hazardous materials on the Shippers
Declaration for Dangerous Goods form. Characteristics vary by aircraft type. Each cargo
compartment floor is limited as to the weight it can carry per square inch or square foot.
Furthermore, the dimensions of cargo must be known to determine the size limits of cargo that
can be placed within each compartment. The potential for movement of hazardous cargo aboard
passenger aircraft is somewhat restrained because the cargo is stowed in compartments. In the
case of both civilian and military cargo aircraft, however, movement pressures are of more
concern. Sideward movement of loads caused by aircraft banking or turning maneuvers must be
considered while aircraft are loaded. A sudden, abrupt ascent or descent might cause some
vertical movement of unsecured cargo; however, lengthwise movement is a primary
consideration. On takeoff, improperly secured cargo is subject to rearward movement. On
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